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태그 보관소: Netplay

Even though the Wii's official library is mostly set, both the GameCube and Wii are entering a new golden age as a popular environment for randomizers, full-game mods, incredible cheat codes, and much more. Stalwarts like the Super Smash Bros. Brawl Mod, Project M have been around for years, but now there are many other communities around various games breathing new life into them. You can find codes to help balance games like Mario Party 5, content mods for Kirby Air Ride that add tons of new rides and hundreds of songs, and trackpacks for Mario Kart Wii that add hundreds of custom tracks to the game. Wiimmfi's also provides their own backup Wi-Fi servers for many unmodified games and their Mario Kart mods!

While most of these mods can be enjoyed on a hacked Wii, many users rely on Dolphin in order to play them. Emulating these mods can be quite the challenge, as they often will do things in ways that game developers would not. Assumptions that Dolphin makes can often be broken and certain features that mod developers use can be extremely slow or downright unreasonable to emulate. In the case of Wiimmfi's Mario Kart Fun Packs, the mod creators have put in work over the years to improve their experience in Dolphin and even support emulated users playing alongside console users online... so long as you're willing to dump and use your Wii's NAND. Earlier this month, a slight change to Wiimmfi's online networking broke Dolphin support without affecting real Wii Consoles. Not wanting to leave their emulated users high and dry, they reported the bug to us.

delroth quickly took up the mantle of investigating the bug with assistance from the Wiimmfi team. Within a few hours, the cooperation paid off as the list of probable causes was narrowed down to one annoying feature: The Instruction Cache. Dolphin pretty much has no ability to emulate the GC/Wii CPU data cache and likely never will due to the performance implications, but Dolphin does have some ability to emulate the instruction cache, though it's best to avoid testing the emulator. This is normally not a problem with retail games because it's rather bad form for a game to rely excessively on cache quirks, unless they were intentionally trying to break an emulator. There are occasionally games that inadvertentlyrely on cache behavior, that's something to tackle on another day. Dolphin's emulation of the instruction cache is normally good enough and almost nothing relies on data cache.

Mods are different; developers are usually working on a blackbox and don't have the same level of familiarity with the hardware. Unless they specifically tested codes on both Dolphin and Wii, there's a chance they wouldn't even know something was broken. There have been many issues reported around mods that, while Dolphin is at fault, we really don't have any recourse for the users afflicted. If a mod doesn't care about running on Dolphin and uses dcache or perhaps another annoying feature, there isn't much we can do but shrug it off.

In the case of Wiimmfi's server, through cooperation from both sides, we were able to find the cache coherency issue and fix it serverside! Users who already have the latest version of the mod don't have to do anything except try to connect. If you're looking for a more detailed explanation of what was going wrong (as it's rather interesting,) you can find delroth's full writeup on the issue tracker.

In order to track down behavior like this in the future, delroth also added game quirk reporting to Dolphin's data collection service, so Dolphin will now automatically let us know what games are instruction cache sensitive in the manner that broke this particular mod. With that, we also have a lot of other exciting changes this month, so now it's time to dive into this month's notable changes!

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One of the most interesting challenges of developing an emulator is that both the target hardware and most of the target software start out as black boxes. As often mentioned within emulation circles, the first step to developing an emulator for a console is getting unsigned code running on real hardware. While running unsigned code on the GameCube can be a bit of a pain, requiring custom hardware or a mixture of the broadband adapter and certain games, the Wii has one of the most robust homebrew environments of any console. Just about anyone can download devkitpro, write their own homebrew, and run it on the Wii.

The truth is that Dolphin is mostly used as an emulator for retail games, but it can also be a useful step for testing homebrew and hacks. After all, when running in Dolphin, users can pause execution, dump RAM, and poke memory without the need for a USB Gecko. While the golden age of Wii homebrew has long passed, several game hacks are still under active development and the Wii remains one of the easiest game consoles to jump into and develop software. Because homebrew can rely on behaviors that games wouldn't ever want to do, even the simplest of projects can stumble into emulator bugs.

Developers kind enough to make their homebrew open source give Dolphin developers an interesting way of debugging issues. It's one of the rare cases where the software being debugged isn't a black box! This greatly cuts down how much effort and expertise is needed to debug what is happening in an issue - instead of mapping out what a game is doing through assembly, we can just look at the source code! Users who write tests that break Dolphin and provide source code give us a much easier look than trying to reverse-engineer what closed source software is doing.

This month, two bugs were discovered that, to our knowledge, do not affect any retail software! Thanks to homebrew projects, these bugs are now a thing of the past. In addition to that, Dolphin on Android has seen a myriad of improvements since our article earlier this month, and netplay saw some new features to make setting up games easier along with a new mode to reduce latency in three/four player matches!

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On July 13th, 2008, Dolphin went open source, now just over ten years ago. While it could be easy to drift off into how much things have changed... there's one particular feature that has never quite lived up to the hype despite debuting that very same year - netplay.

As surprising as it may sound Dolphin Netplay has been around since the emulator went open source. For roughly a decade, users have tried their hand at taming the beast of synchronizing multiple instances of a GameCube and Wii despite their relative complexities. Netplay allows users to run the same instance of game on multiple computers by having two or more emulators in the exact same state, only transferring inputs between one another. By staying in lockstep like this, theoretically the emulators' states will never diverge assuming perfect determinism. This would allow people across the world to play a game together, even if it only featured local multiplayer on the console.

The problem has always been attaining that determinism. Back in the early days of netplay, it didn't especially matter what settings were used; Dolphin wasn't deterministic enough to stay in lockstep for very long. Then in the early days of the 3.0 era, it was finally possible to stay synced - if you were willing to sacrifice audio and performance. Early netplayers would hack up Dolphin to reduce requirements with 30 FPS hacks to Super Smash Bros. Melee, hacks to LLE audio to make it slow down less during attacks, and much more.

Despite the stutters and desyncs, some serious Melee players saw the potential and kept with the project. It wasn't until New-AX-HLE Audio (part 2) hit Dolphin that audio was both performant and deterministic enough to use in netplay. By the time Dolphin 4.0 rolled around, netplay had become a staple for Melee users and could be used by advanced users willing to suffer through some annoying quirks.

In the last few years, a focus has gone toward adding highly requested features to make netplay easier to use. Dolphin's STUN service allows some users who cannot port-forward play on netplay without issues, saves can be disabled to make synchronizing party games easier. But the one constant is that despite all these advances, simply getting netplay to work was a chore and crashes were common even if you did everything right.

Getting netplay into a more user-friendly state has been quite the process. In July, we saw some of the most drastic changes to netplay that we've seen in the past couple of years! Emulated Wii Remotes also saw huge usability improvements and some non-NVIDIA Android devices will finally be able to use Dolphin's Vulkan backend. If that wasn't enough, spycrab0 delivered some very big improvements to the DolphinQt GUI to give a new way to display your favorite games in the gamelist. Let's not delay any longer, please enjoy this month's Dolphin Progress Report.

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While an emulator's primary job is to emulate, there's usually a lot more that goes into a good emulator. For Dolphin, it may feel like a lot of work has gone toward luxury features and optimizations rather than improving accuracy and compatibility. For example, Ubershaders is a wonderful, game-changing feature, but it can't fix any bugs in emulation. With another of those huge features on the brink, it's important to highlight that no one has forgotten about Dolphin's weaknesses - it's just getting harder to fix them. Most of the games that no longer work in Dolphin either require better timings (which slow emulation and need to be hardware tested,) or rely on undocumented behaviors that have to be painstakingly sought out, rather than stumbled upon.

Case in point, fixing one of those cases could require weeks of devotion and every development tool in our arsenal just to locate the bug. With Red Steel, developers ended up having to reverse engineer why an engine bug affected Dolphin but not the Wii.

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July and August have been busy on the blog. On top of working on this Mega Progress Report, two feature length articles had to be made after developers selfishly merged several huge, highly anticipated features without considering that it makes work for us here at the blog! Well, the extra work-load is well worth having the incredible Ubershaders and support for Dragon Quest X!

But even beyond those two massive articles, we've been hard at work keeping up with everything else going on because this is going to be a big one. Adding to that someone on the blog staff thought this month of all months would be a good idea to try and harness the power of the blog to get extra testing on some old issues. So buckle up, this is going to be a long read!

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As the twilight of the Dolphin 4.0 era approaches, code cleanup and regression hunting have become a high priority, fixing the serious and minor issues that have cropped up over the past year and a half that remain unaddressed. From remedial problems such as INI issues to Real Wiimotes issues on OS X, a lot of those important minor issues have been tackled. As if that wasn't enough, there are still exciting developments within several core features to keep users satiated in this month's Progress Report.